ASSESSING BRUCELLOSIS AND BOVINE TUBERCULOSIS SEROPREVALENCE IN WILD BOAR IN THE NETHERLANDS (2018–20) USING COMMERCIALLY AVAILABLE ELISAS

Increasing spatial overlap between wild boar (Sus scrofa), humans, and domestic animals emphasizes the need for targeted disease monitoring in wild boar to inform national risk assessments. Wild boar may act as spillover and reservoir hosts for the bacteria causing brucellosis and bovine tuberculosis (bTB), diseases for which the Netherlands maintains an official disease-free status in livestock. Brucella suis biovar 2 has previously been detected in hunted wild boar in the Netherlands, suggesting a northward spread in wild boar within the country. Exposure of wild boar to Mycobacterium bovis in the Netherlands has not previously been investigated. This study aimed to estimate the seroprevalence of Brucella spp. and M. bovis in wild boar populations in the Netherlands during 2018–20 by using biobanked serum samples from an existing disease monitoring program. Commercial indirect ELISAs were used to determine apparent seroprevalence, and Bayesian latent class models were applied to estimate true seroprevalence while accounting for imperfect test performance. For Brucella spp., no increase in seroprevalence was detected compared with previous estimates in Dutch wild boar populations. Nevertheless, spatial and temporal clustering of seropositive results suggested heterogeneity in exposure, with an estimated true seroprevalence of 8.4% in the province of Limburg in 2020. For M. bovis, serologic reactivity against the antigens used in the ELISAs was detected in a limited number of sera. The findings of this study support a risk assessment to evaluate whether current national surveillance approaches for brucellosis and bTB in livestock and wildlife in the Netherlands are adequate or require strengthening or further development. Strengthening early detection at the wildlife-livestock interface is essential to safeguard animal and public health and to maintain the Netherlands' disease-free livestock status.